FR2809272A1 - Cellular radio communications network downlink control having multiframes with digital word blocks network allocation time periodic and mobile units transmitting. - Google Patents

Abstract

The real time digital word packet transmission system has a number of multiframes with digital word blocks (B0-B11) transmitting to several mobile units. The network allocates specific blocks periodic in time to each unit.

Description

The present invention relates to the field of communication management in cellular radio networks, in particular downlink transmissions to mobile stations or terminals forming part of these networks and upstream transmissions of said mobiles to said networks.

The present invention relates to a real-time packet data transmission method and a cellular radio communication network implementing this method.

Herein, the term "amount" used to designate a transmission or transmission channel of one or more mobile terminals to the network ("uplink") and "descendant" to refer to a transmission or transmission channel of the network to one or more mobile affiliated with it ("downlink").

Currently, in the context of the transmission of packet information, for example according to the standards known as G.P.R.S. (for "General Packet Radio Service"), E.G.P.R.S. (for "Enhanced General Packet Radio Service") G.E.R.A.N. (for "GSM / EDGE / RAN"), it is common for several terminals or mobile stations to be multiplexed on the same transmission channel or the same downstream channel (PDCHID), ie say that the network sends a plurality of blocks of information on at least one slot or time slot (the) allocated simultaneously to a plurality of mobile terminals, each of which may be assigned one or more slots ( s) or time window (s).

Similarly, in these standards, several terminals or mobile stations can also be multiplexed on the same transmission channel or the same uplink channel (PDCH / U), that is to say a plurality of information blocks from a plurality of mobiles are transmitted over at least one interval or at least one common time slot (the) which is simultaneously allocated to them, towards the network.

To ensure the management of common transmission resources and avoid conflicts, it is then necessary, in the aforementioned contexts, to allocate the blocks in upstream and downstream transmission. to be able to carry out transmissions with a data flow in real time, it is necessary to have a substantially constant bit rate and preferably a shortest possible transmission delay.

Different classes of traffic have been proposed for the G.E.R.A.N. standard, of which at least two, namely those known under the designations "Conversational Traffic Class" and "Streaming Traffic Class", are oriented towards a traffic in real time.

With regard to the three aforementioned standards, two modes of allocation or allocation of blocks have been proposed, for the upstream transmissions, namely a dynamic allocation mode and a fixed allocation mode, both with disadvantages and limitations that make them unsuitable for real-time transmission.

Thus, the dynamic allocation mode is characterized in that the mobile transmits a block or a group of four blocks on a packet data transmission channel (PDCH) after detection of a rising transmission state indicator ( USF) allocated on the downstream side for each allocated PDCH channel.

To ensure a constant bit rate, it is necessary in such dynamic allocation mode, not allowing an advance allocation of a USF message to a mobile, to periodically allocate a specific USF for each mobile, any defect in however, the allocation period induces a variable bit rate on the air interface, which does not satisfy the constant bit rate requirements for real-time traffic.

This mode of attribution is therefore, by its very nature, inappropriate to guarantee the conditions required for real-time transmission and its implementation can be tricky and tedious for the network.

The fixed allocation mode is characterized in that the network sends to each mobile concerned a multiplexed upstream transmission, prior to the transmission of the data or information blocks, a message designating the different allocated allocation blocks and each bit of which allows a considered mobile to determine whether a given block is part or not blocks allocated to it an allocated time slot or all allocated time slots for said upward transmission. This resource allocation message contains a field designated by the term "ALLOCATION_BITMAP" in GSM Recommendations No. 04.18 and No. 04.60 of the UST.S.I.

Although it is better suited to real-time streaming than the dynamic allocation mode, this fixed allocation mode nevertheless has a major drawback, namely that, due to the necessarily finite length of the "ALLOCATION BITMAP" field. ", the network will carry out a periodic reassignment of a new field" ALLOCATION_BITMAP "for each given mobile.

Thus, when the limited set of allocations defined by each consecutive "ALLOCATION_BITMAP" field expires, the radio resource is requested to send a new "ALLOCATION BITMAP" field and therefore a constant bit rate can not be used. provided for the transmission of data (additional bandwidth required for this signaling). It is then mandatory to use high capacity buffers at the mobile to try to regulate the flow, with negative consequences for the use of the memory of the mobile and the size necessary for the latter, and on the resulting delay in the transmission.

moreover, it should also be noted that this fixed allocation mode currently exists only for uplink transmissions and can only be applied to packet transmission channels (and not to the control channel dedicated to the circuit - DCCH) .

A problem with the present invention is to overcome the drawbacks of existing solutions and to propose a mechanism for allocating or allocating shared transmission resources between several mobiles in networks of the aforementioned type for a real-time data transfer with a network. short time substantially constant. This mechanism should be simple to implement, take optimal advantage of the bandwidth, be applicable to upstream and downstream packet transmissions and in particular be compatible with G.P.R.S. standards. and E.G.P.R.S., as well as possibly G.E.R.A.N.

To solve this problem, the present invention proposes a method of real-time data transmission, in packets, between a network and a mobile radio terminal, the transmission being carried out on a plurality of multiframes each comprising a given number of blocks, characterized in that, prior to each transmission, the network allocates to the terminal or to each terminal considered specific blocks distributed substantially periodically in time.

This allocation can advantageously be achieved by sending a single message at the beginning of transmission of the network to the terminal considered defining the blocks and their periodicities and valid for the duration of the transmission.

According to a preferred embodiment of the invention, advantageously applicable in the case of multiplexed mobile terminals one or more time interval (s) and a transmission protocol using multifrysts repeating in a predetermined manner including periodically over time, the network sends to the terminal concerned, prior to each transmission, a number a sequence of block numbers (s) located (s) or distributed identically in each multiframe for each time interval ("timeslot") ") allocated and allocated to him / her for the duration of the transmission concerned.

As is apparent from the foregoing, the basic idea of the invention is to exploit the periodic or quasi-periodic recursion of elementary information blocks in the structure of the logical radio channels.

In fact, time division multiple access (TDMA) frames are part of multiframes which are repeated in a predictable manner over time for the mobile terminal and the network.

It is therefore easy to assign to each multiplexed mobile a basic block of radio resource and refer to it by an indicator or an identifier, such as for example a number.

Thanks to the provisions mentioned above, the transmission time decreased and the flow remains constant over time, because of the periodicity of the resources allocated and their predictability for the duration of the transmission.

in addition, the unique assignment at the beginning of transmission avoids the breakage and disruption of the data transmission rate by sending successive assignment messages.

In the case of a two-way communication link between the network and the mobile in question, it must be planned to send to the mobile considered first sequence of block allocation numbers for each time slot allocated in transmission on each transmission channel. packet data and a second sequence of block allocation numbers for each allocated downlink time slot on each packet data channel, two or more sequences being identical or not.

Advantageously, the number or sequence of allocation numbers or allocation blocks in each time slot allocated to a mobile concerned is sent (e) to said mobile terminal, multiplexed one or more interval (s) of time with one or a plurality of other mobile terminals, beginning of packet transmission establishment, together with the assignment of their frequency or their frequency hopping law to their specific common time slot, as a particular sub-allocation for each of said mobile terminals multiplexed.

This under-allocation can, for example, occur, in particular in the case of standards G.P.R.S. and E.G.P.R.S., in the form of a single field of the "ALLOCATION_BITMAP" type of an allocation message valid for the duration of the transmission and avoiding the mobile to wait for a new allocation during transmission.

The allocation or the periodic allocation of blocks specific to a given mobile terminal may, for example, be determined based, in particular, on its possible transmission possibilities in multiple time slots, the bit rate required for the expected data stream, the level of quality of service desired for transmission, in particular the maximum acceptable delay due to transmission, and / or the required degree of reliability and security of the transmission.

The method according to the present invention is particularly suitable for implementation with multiframes having a multiframe configuration 52 ("52 multiframe").

However, it may also be applied in relation to multiframes having a multiframe configuration 51 ("51 multiframe"), the mobile terminals being of the so-called class A type (mobile terminals that can perform in parallel a packet transfer and a connection circuit service), in particular for carrying out packet transmission on one or more control channels dedicated to the circuits (DCCH). By way of illustrative but nonlimiting example, a particular application of the invention in relation with the G.P.R.S. standard is described below.

In the context of the latter, the network assigns to the mobile a packet data transmission channel (PDCH) defined by a frequency or a law of frequency hops and one or more time slots ("timeslot").

All PDCH channels are transmitted in a "multiframe" multiframe configuration as shown in the accompanying drawing herein. This multiframe is formed of twelve blocks of data BO to B 11 (each formed of four TDMA frames) and four empty frames (1).

Each block may be shared between several mobiles on each upstream PDCH channel and / or each downstream PDCH channel of the aforementioned multiframe.

According to the example shown in the appended drawing, the network can assign to a first mobile <B> MS 1 </ B> a frequency f1 and a time slot TSO for an upstream packet transfer and allocate it simultaneously the blocks BO and B7 of the multiframe, which means that said mobile MS1 will always transmit in the blocks BO and B7 on the time slot TSO and at the frequency f1.

Then, the network can allocate, also in uplink transmission, the same torque (frequency f1 / time slot TSO) a second mobile and allocate it for example the blocks B2, B9 and B10.

Finally, the network can also allocate, also in uplink transmission, the same torque (frequency f1 / time slot TSO) to a third mobile and allocate it for example blocks B3, B5, B6 and B8.

Of course, these allocations and allocations are repeated for each multiframe.

To achieve these allocations and allocations, the network can for example send a "bitmap" in a resource allocation message for one or more slots allocated in uplink and / or a "bitmap" in a resource allocation message for one or more time slots allocated in downlink transmission. Thus, a given time interval TS may be assigned a block allocation by means of indicators or flags of the type (i, j) with i varying from 0 to 7 and with j varying from 0 to 11.

In this case, a "bitmap" addressed to a mobile (for an upward or downward transmission) and including a sequence such indicators can be interpreted in the following way * in upward transmission - if TS (i, j) = 1, then the concerned mobile will transmit in the TS interval of the block Bj, - if TS (i, j) = 0, then the mobile concerned will not transmit in the range of the block Bj, * in downlink transmission - if TS (i, ') = 1, then the mobile concerned will receive in the TS interval of the block Bj, - if TS (i, j) = 0, then the mobile concerned will not receive in the TS interval of the block Bj.

It will be noted that the method according to the invention can also be combined with a so-called fixed or dynamic type allocation mode, the network being able to multiplex several mobiles on the same uplink resource by using different allocation modes.

The network may, for example, allocate an allocation (f1, TSO, USF) to a first mobile and an allocation (f1, TSO, allocation of blocks BO and B7 according to the invention) to a second mobile, the network not being authorized. delivering a USF indicator to the first mobile for the BO and B7 blocks in the time interval TO of the frequency f1.

The present invention also relates to a radio telecommunication cellular network comprising a plurality of geographically distributed fixed stations and a plurality of mobile terminals that can be put in communication with each other for mobile upstream transmission to the network and / or downlink transmission from the network to the networks. mobile, said data transmissions taking place in real time in packets on a plurality of multiframes each formed of a given number of blocks and each of which can be shared between several mobile terminals, characterized in that each mobile terminal is allocated or allocated, during the establishment of a transmission and for the duration of said transmission, specific blocks distributed substantially periodically over time. Preferably, the allocation or allocation by the network of mobile-specific blocks is carried out according to the method described above and the transmission protocol is of a type chosen from the group formed by the protocols known respectively under the GPRS designations, EGPR and GERAN

Finally, the subject of the invention is also a mobile mobile radio terminal, possibly forming part of a network as described above, characterized in that it is adapted for implementing the data transmission procedure in accordance with FIG. real time described above.

Thanks to the invention, it is possible to propose a transmission method enabling the network to flexibly distribute the data volume to be transmitted over several time intervals for upstream and / or downstream transmission, while multiplexing several mobiles on one or more channels. of transmission amounts or descendants and ensuring a constant bit rate and low transmission delays, well suited to real-time flow data transmissions.

In addition, the transmission method may also be applied to dedicated traffic channels.

It may indeed be advantageous to use for example a dedicated control channel (DCCH) for packet transmission when a dedicated traffic channel is already in use, without however soliciting said dedicated control channel. continuously when the estimated packet transmission rate is low.

Of course, the invention is not limited to the embodiment described and shown in the accompanying drawing. Modifications are possible, particularly from the point of view of the constitution of the various elements or by substitution of technical equivalents, without departing from the scope of protection of the invention.

Claims (3)

A method for real-time data transmission, in packets, between a network and at least one mobile radiocommunication terminal, the transmission being performed on a plurality of multiframes each comprising a given number of blocks, characterized in that, prior to each transmission, the network allocates terminal or each terminal considered specific blocks distributed substantially periodically in time. 2. Method according to claim 1, characterized in that, in particular in the case of multiplexed mobile terminals one or more time interval (s) and a transmission protocol using multiframes repeating in a predetermined manner including periodically in time, the network sends to the terminal concerned, prior to each transmission, a number or a sequence of block numbers (s) located (s) or distributed identically in each multiframe on each time slot allocated and which is / are attributed to it for the duration of the transmission concerned. 3. Method according to claim 2, characterized in that it consists in sending to the mobile considered a first sequence of block allocation numbers for each time slot allocated in transmission up on each packet data transmission channel a second a sequence of block allocation numbers for each time slot allocated in downlink transmission on each packet data channel, the two sequences being identical or different. Method according to any one of claims 2 and 3, characterized in that the number or sequence of allocation numbers or allocation blocks in each time slot allocated to a given mobile is sent (e) to said mobile terminal multiplexed over one or more time intervals with one or more other mobile terminals, at the beginning of the packet transmission establishment, together with the assignment of their frequency or frequency hopping law and their interval common specific times, as a particular sub-allocation for each of said multiplexed mobile terminals. 5. Method according to any one of claims 1 to 4, characterized in that the allocation or the periodic allocation of specific blocks to a given mobile terminal is determined based in particular on its possible transmission possibilities in time intervals. multiple, the data rate expected for the expected data, the level of quality of service desired for transmission, in particular the maximum acceptable delay due to transmission and / or the required degree of reliability and security of the transmission. 6. Method according to any one of claims 1 to 5, characterized in that the multiframes have a configuration of the multiframe type 52. 7. Method according to any one of claims 1 to 5, characterized in that the multiframes have a configuration of the multiframe type 51, the mobile terminals being of the so-called class A type. 8. Radio telecommunication cellular network comprising a plurality of fixed stations geographically distributed a plurality of mobile terminals able to be put in communication with each other for an upward transmission of the mobiles towards the network and / or a downlink transmission from the network to the mobiles, said data transmissions taking place in real time in packets on a plurality of multiframes each formed of a given number of blocks and which can each be shared between several mobile terminals, characterized in that that each mobile terminal is allocated or allocated, the establishment of a transmission and for the duration of said transmission, specific blocks distributed substantially periodically over time. 9. Network according to claim 8, characterized in that the allocation or assignment of specific blocks is performed according to the method described in any one of claims 2 to 7. 10. Network according to any one of claims 8 and 9, characterized in that the transmission protocol is of a type chosen from the group formed by the protocols known respectively as GPRS, EGPRS and G.E.R.A.N. 11. mobile mobile radio terminal, possibly forming part of a network according to any one of claims 8 '10, characterized in that it is adapted for implementing the method of real-time data transmission according to the any of claims 1 to 7.